1. Field of the Invention
This invention relates to a liquids-solids separator and in particular to a separator in a gas scrubbing system for removing sulfur oxides and particulate material from industrial stack gases.
2. Description of the Prior Art
As exemplified by U.S. Pat. No. 3,989,465 which shows a wet gas scrubbing apparatus for removing sulfur oxides from hot industrial stack gases, the typical wet scrubbing system provides that stack gases be directed through a scrubbing tower wherein a scrubbing spray of liquid reactant is continuously injected into the gas flow by a series of nozzles within the tower. During the scrubbing process, the reactant liquid neutralizes and entrains the sulfur oxides in the gases as well as flyash and other particulate solids to form a liquids-solids suspension which is in turn collected and directed to flow through a reaction tank connected to or integral with the scrubbing tower. As the suspension flows through the reaction tank, particulate solids, including scale resulting as a precipitate of the scrubbing process, settle out of the suspension for subsequent removal from the tank as a slurry or sludge, and concurrently, additional reactant materials are added to regenerate the reactant liquid. Thereafter, as the regenerated reactant flows from the tank, it is pumped back to the scrubbing tower and again injected into the gas flow to maintain the scrubbing process.
In scrubber arrangements such as the foregoing, it is particularly desirable to maintain turbulence in the reactant liquid while it is in the reaction tank. This promotes homogeneity of the liquid to insure its complete regeneration while accommodating close control of the regenerated liquid's pH as it leaves the tank to reduce the possibility of acid attack in the scrubber as well as the formation of excessive scale or precipitates in the scrubbing tower. However, this reduces the settling rate and thus limits removal of particulate solids from the suspension in the tank such that it has been necessary to provide a screen or similar filtering arrangement across the return line provided to convey the regenerated reactant liquid back to the scrubbing tower to prevent clogging of the nozzles in the tower. Thus, while this type of arrangement accommodates removal of the solids retained in the regenerated reactant liquids, experience has shown that it must be very closely monitored by operating personnel and frequently cleaned or replaced during normal operation of the scrubbing system.